A large portion of the seating industry has begun to manufacture chairs in preassembled sections. The sections generally are a base, a seat post assembly including a seat post, and a seat member. A common chair configuration has the seat post assembly being attached to the seat member and the base having a base tube fitted so as to enclose the seat post. The base can be as desired for the particular application, e.g., wheeled or stationary.
The seat member and the seat post assembly can be varied also to add features such as rocking mechanisms, swivel or tilt mechanisms, lumbar supports, height positioning controls, and other chair controls. A wide variety of chairs are manufactured by varying the combination of base, seat post assembly, and seat member used.
Typical chair construction employs bushings. The seat member is joined to the base. Bushings are generally press fitted into the base tube, which is attached to the base. However, if there is any variation in the inner diameter of the base tube, variations in the inner diameter of the bushings result. Variations in the inner diameters of the bushings can make it impossible to insert the seat post unless a secondary machining operation is done on the installed bushings.
It is possible to avoid this secondary machining operation if the inner diameter of the base tube is accurate enough. To be as accurate as required, the base tube must be drawn over a mandrel whereupon, when the bushings are pressed fitted into the base tube, the inner diameters of the bushings remain constant and the seat post can be pressed into the bushings. This alternative is expensive because of the tight tolerances.
Industry practice is to preassemble as much of the chair as possible while keeping the preassembled units compact for shipping and warehousing. For example, after the bushings are pressed in the base, as discussed above, the chair can be shipped as two units, a base and a seat member with a seat post attached.
Thus, it can be appreciated that it would be desirable to have an improved post bushing for use in chair assemblies, as well as in other applications. The improved post bushing should lessen the need to maintain tight tolerances, while allowing preassembly of various components into preassembled units.